Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, USA.
Bioproducts Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA, USA.
Plant Biotechnol J. 2020 Sep;18(9):1955-1968. doi: 10.1111/pbi.13355. Epub 2020 Feb 19.
Drought stress is the major limiting factor in agriculture. Wheat, which is the most widely grown crop in the world, is predominantly cultivated in drought-prone rainfed environments. Since roots play a critical role in water uptake, root response to water limitations is an important component for enhancing wheat adaptation. In an effort to discover novel genetic sources for improving wheat adaptation, we characterized a wheat translocation line with a chromosomal segment from Agropyron elongatum, a wild relative of wheat, which unlike common wheat maintains root growth under limited-water conditions. By exploring the root transcriptome data, we found that reduced transcript level of LATERAL ROOT DENSITY (LRD) gene under limited water in the Agropyron translocation line confers it the ability to maintain root growth. The Agropyron allele of LRD is down-regulated in response to water limitation in contrast with the wheat LRD allele, which is up-regulated by water deficit stress. Suppression of LRD expression in wheat RNAi plants confers the ability to maintain root growth under water limitation. We show that exogenous gibberellic acid (GA) promotes lateral root growth and present evidence for the role of GA in mediating the differential regulation of LRD between the common wheat and the Agropyron alleles under water stress. Suppression of LRD also had a positive pleiotropic effect on grain size and number under optimal growth conditions. Collectively, our findings suggest that LRD can be potentially useful for improving wheat response to water stress and altering yield components.
干旱胁迫是农业的主要限制因素。小麦是世界上种植最广泛的作物，主要种植在干旱少雨的雨养环境中。由于根系在水分吸收中起着关键作用，因此根系对水分限制的响应是增强小麦适应性的一个重要组成部分。为了发现提高小麦适应性的新的遗传资源，我们对一条来自小麦野生近缘种长穗偃麦草的染色体片段易位系小麦进行了鉴定，该易位系与普通小麦不同，在水分有限的条件下能维持根系生长。通过探索根系转录组数据，我们发现，在长穗偃麦草易位系中，LRD 基因的转录水平在水分有限的条件下降低，从而使其具有维持根系生长的能力。与受到水分亏缺胁迫而上调的小麦 LRD 等位基因不同，LRD 基因在受到水分限制时，其长穗偃麦草等位基因下调。在小麦 RNAi 植株中抑制 LRD 的表达赋予其在水分限制下维持根系生长的能力。我们表明，外源赤霉素（GA）促进侧根生长，并提供证据表明，GA 在介导普通小麦和长穗偃麦草等位基因在水分胁迫下 LRD 的差异调节中起作用。LRD 的抑制也对最佳生长条件下的粒大小和数量产生了积极的多效性影响。总的来说，我们的研究结果表明，LRD 可以潜在地用于提高小麦对水分胁迫的响应和改变产量构成。
